High temperature vessels of the type for which the present invention is particularly efficacious include ladles for molten metal, tilting furnaces, rotary kilns or other similar vessels lined with a refractory material and having a curved interior cross-section, illustrative of which is that disclosed in U.S. Pat. No. 4,989,843 granted to William E. Dietrich et al on Feb. 5, 1991. Because of the extremely high operating temperature of such vessels, a number of problems have arisen in utilizing the proposals of the prior art. Thus, for example, refractory materials are subject to thermal expansion and contraction, thermal shock, and wear abrasion, all of which may be exacerbated by molten material impurities such as slag.
In addition to the foregoing, and in part due to considerations relating to the extremes of thermal expansion and contraction resulting from the extreme temperature excursions, there has been a tendency for refractory bricks or the like to loosen, fracture or dislodge from their installed positions and either drop into the contents of the vessel or to fall outwardly therefrom when the vessel is tilted or inverted to empty its contents.
High temperature vessels of the type contemplated hereby and referred to above, typically include a metal outer shell, an inner lining composed of a plurality of aligned or superimposed courses of refractory brick and an opening at one end of the vessel. Unless provision is made at the open end of the vessel for retaining the refractory bricks securely in place, forces exerted on the refractory bricks in a direction toward the open end of the vessel may cause one or more of the courses of refractory bricks to fall out at the open end.
Proposals have heretofor been made for retaining refractory linings in place, but all of these prior proposals have had disadvantages. As referred to in the foregoing U.S. Pat. No. 4,989,843, one such prior art retaining structure was in the form of steel angle iron having one flange attached to the inner surface of the outer shell of the ladle adjacent the open end and another flange unenclosed by refractory material extending from its junction with the one flange at the open end of the ladle. This other flange extended radially inward with respect to the ladle interior a distance substantially the same as that to which the refractory material extended, and there was a layer of refractory ramming material sandwiched between the nearest course of refractory brick and one surface of the inwardly extending flange of the steel angle iron. When the ladle was wholly or substantially inverted, the aligned courses of refractory brick were supported by the inwardly extending flange of the steel angle iron, thus preventing the refractory material from falling out of the inverted ladle. However, the foregoing and other types of prior art retaining structures exhibited problems when subjected to preheating or extreme temperature excursions. As is known to those skilled in the art, a preheater is typically employed to heat the refractory material to a temperature near that to which it will be subjected when encountering molten materials so as to reduce the danger of rupture or failure due to thermal shock. Typically, hot gases are directed from the preheater to the open end of the vessel into its interior. Hot exhaust gases escaping from the interior during the preheating operation encounter the prior art retaining structures, and because a portion of the metal thereof typically was exposed to such gases and was not entirely enclosed by refractory, a portion was excessively heated by the hot exhaust gases, eventually resulting in structure deformation or failure. In such event, the effectiveness of such retaining structures was substantially reduced or eliminated.
As further described in the above U.S. Patent, attempts to solve the foregoing retaining structure problem resulted in a different orientation of iron materials utilized in the retaining structure so as to make it practical to entirely cover it with a layer of refractory ramming material reinforced with other elements. However, such refractory ramming material was thus exposed to wear, thereby requiring more frequent maintenance.
Still other problems were inherent in prior art proposals. Thus, for example, in the heretofore described prior art proposals, problems were encountered when it became necessary to replace worn refractory bricks or courses of refractory materials. For this purpose a jack hammer was primarily employed. Because of the vessel geometries and the attendant difficulties in effective positioning and control of the jack hammer, damage often resulted to the retaining structures thereby requiring their replacement.
The above mentioned U.S. Pat. No. 4,989,843 sets forth proposals for ameliorating the problems inherent in the preexisting prior art. According to the proposals of that patent, a rounded protrusion was provided near the inner circumference of the vessel opening, and a course of refractory brick was installed in mating engagement therewith. Each of the refractory brick in such course was provided with a rounded recess that upon installation was in mating engagement with the circumferential protrusion, thus providing for the locking of each of the refractory brick in such circumferential course to the circumferential protrusion and consequently through it to the main body of the vessel exterior. However, it has been found in practice that due to the extreme temperature variations and consequent expansions and contractions, there has been a tendency for such special notched refractory brick to fracture, thereby degrading or destroying the effectiveness of the circumferential protrusion from retaining such brick in their appointed locations. Accordingly, there has continued to be a need for an improved construction which provides for secure retention of such refractories in their appointed positions while at the same time avoiding the foregoing problems of the prior art proposals.